Abstract: A “dirty bomb” is one
type of a “radiological dispersal device” (RDD) that combines a conventional
explosive, such as dynamite, with radioactive material.

The terms dirty bomb and RDD are often used interchangeably in the media. Most
RDDs would not release enough radiation to kill people or cause severe illness
- the conventional explosive itself would be more harmful to individuals than
the radioactive material. However, depending on the scenario, an RDD explosion
could create fear and panic, contaminate property, and require potentially
costly cleanup. Making prompt, accurate information available to the public
could prevent the panic sought by terrorists.

A dirty bomb is in no way similar to a nuclear weapon or nuclear bomb. A
nuclear bomb creates an explosion that is millions of times more powerful than
that of a dirty bomb. The cloud of radiation from a nuclear bomb could spread
tens to hundreds of square miles, whereas a dirty bomb’s radiation could be
dispersed within a few blocks or miles of the explosion. A dirty bomb is not a
“Weapon of Mass Destruction” but a “Weapon of Mass Disruption,”
where contamination and anxiety are the terrorists’ major objectives.

Impact of a Dirty Bomb
The extent of local contamination would depend on a number of factors,
including the size of the explosive, the amount and type of radioactive
material used, the means of dispersal, and weather conditions. Those closest to
the RDD would be the most likely to sustain injuries due to the explosion. As
radioactive material spreads, it becomes less concentrated and less harmful.
Prompt detection of the type of radioactive material used will greatly assist
local authorities in advising the community on protective measures, such as
sheltering in place, or quickly leaving the immediate area. Radiation can be
readily detected with equipment already carried by many emergency responders.
Subsequent decontamination of the affected area may involve considerable time
and expense.

Immediate health effects from exposure to the low
radiation levels expected from an RDD would likely be minimal. The effects of
radiation exposure would be determined by:

1. The amount of
radiation absorbed by the body;2. The type of radiation (gamma,
beta, or alpha);3. The distance from the radiation
to an individual;4. The means of exposure-external or
internal (absorbed by the skin, inhaled, or ingested); and5. The length of time exposed.

The health effects of radiation tend to be directly proportional to
radiation does. In other words, the higher the radiation does, the higher the
risk of injury.

Protective Actions
In general, protection from radiation is afforded by:

1. Minimizing the time
exposed to radioactive materials;2. Maximizingthe
distancefrom the source of radiation; and3. Shielding from external exposure
and inhaling radioactive material.

More detailed guidance is provided in the questions and answers at the
end of this Backgrounder.

Sources of Radioactive MaterialRadioactive materials are routinely used at hospitals,
research facilities, industrial and construction sites. These radioactive
materials are used for such purposes as diagnosing and treating illnesses,
sterilizing equipment, and inspecting welding seams. The Nuclear Regulatory
Commission together with 33 “Agreement” States, which also regulate radioactive
material, administer over 21,000 licenses of such materials. The vast majority
of these materials are not useful as an RDD.

Control of Radioactive MaterialNRC and state regulations require owners licensed to
use or store radioactive material to secure it from theft and unauthorized
access. These measures have been greatly strengthened since the attacks of
September 11, 2001. Licensees must promptly report lost or stolen high-risk
radioactive material. Local authorities also assist in making a determined
effort to find and retrieve such sources. Most reports of lost or stolen
material involve small or short-lived radioactive sources not useful for an
RDD.

Past experience suggests there has not been a pattern of collecting such
sources for the purpose of assembling an RDD. It is important to note that the
radioactivity of the combined total of all unrecovered sources over the past 5
years (when corrected for radioactive decay) would not reach
the threshold for one high-risk radioactive source. Unfortunately, the same
cannot be said world-wide. The U.S. Government is working to strengthen
controls on high-risk radioactive sources both at home and abroad.

Risk of Cancer
Just because a person is near a radioactive source for a short time or gets a
small amount of radioactive dust on himself or herself does not mean he or she
will get cancer. Any additional risk will likely be extremely small. Doctors
specializing in radiation health effects will be able to assess the risks and
suggest mitigating medical treatment, once the radioactive source and exposure
levels have been determined.

There are some medical treatments available that help cleanse the body
of certain radioactive materials. Prussian blue has been proven effective for
ingestion of cesium-137 (a radioactive isotope). In addition, potassium iodide
(KI) can be used to protect against thyroid cancer caused by iodine-131
(radioactive iodine). However, KI, which is available as a “over the counter”
offers no protection to other parts of the body or against other radioactive
isotopes. Medical professionals are best qualified to determine how to best
treat symptoms (United
States Nuclear Regulatory Committee, 2011).